Abstract: A structure is provided for adjusting the lateral displacement of an outer second boom relative to a first, or base boom which receives and supports the second boom for telescoping movement relative thereto. A box-like retainer structure is provided to receive a pair of wear blocks which project from the retainer structure on each side of the second boom and are adapted to slidingly engage the inner surface of the sides of the base boom. A pair of threaded adjustment blocks are provided, one block inwardly of and adjacent each wear block for retaining the wear blocks against the base boom. Each adjustment block is threadingly engaged with a separate bolt and the distal end of each bolt opposite the adjustment block is retained within a bore of an upstanding wall to prevent each bolt from moving laterally relative to the second boom but to permit rotation of the bolts.